1. Field of the Invention
The present invention relates to a composition for providing a xe2x80x9cnon-wettablexe2x80x9d coating, and a method of preparing the same. The invention also relates to articles coated with such a composition, and methods for their preparation.
2. Discussion of the Background
In the context of the present invention the term xe2x80x9cwettabilityxe2x80x9d refers to the adherence of polar or nonpolar liquids to articles to form a detrimental film; and refers also to the tendency of the articles to retain dusts and soils of all typesxe2x80x94e.g., fingerprints, insect remnants, etc.
The presence of water and/or soils on the articles confers an unattractive appearance. Additionally this can cause changes in the ability to see through the articles and diminishes their transparency, which is particularly detrimental in the case of vehicle and aircraft panes and ophthalmic lenses.
Various types of non-wettable coatings are known.
One known coating can be obtained from fluorinated organosilanes, such as that described in EP 492,545. Another known coating can be obtained from a mixture of a perfluoroalkylsilane and an olefinic fluorinated telomer, as described in EP 452,723.
However, it turns out that the non-wettability of these coatings is subject to thermal degradation. This is a particular problem with vehicle panes which, in addition to ordinary aging effects from various factors, such as atmospheric conditions (humidity and sunlight or other light), are subjected to substantial abrasion, particularly from the impact of particles, such as directly or indirectly from the rubbing of windshield wipers, washing rags, or cleaning squeegees, or violent impingements which may occur.
In order to improve resistance to abrasion, EP 548,775 proposes coatings of the polysilane type having bonds of the type xe2x80x94Sixe2x80x94Oxe2x80x94Sixe2x80x94 and containing fluorinated groups.
However, the nature of these coatings leads to glass panes and the like which are not satisfactory for prolonged use.
Accordingly, one object of the present invention is to provide an article covered with a non-wettable coating which provides improved abrasion resistance and particularly which has non-wettability which is preserved in the face of abrasion.
A further object of the present invention is to provide a method for the production of an article having a non-wettable coating as noted above.
A further object of the present invention is to provide a heat-settable composition which can be used to prepare a hydrophobic, oleophobic, abrasion resistant coating, suitable for application to substrates such as glass or polymeric ophthalmic lenses.
These and other objects of the present invention have been satisfied by the discovery of a heat-settable composition for a coating which is hydrophobic, oleophobic and resistant to abrasion, comprising a hydrolyzate obtained from a solution comprising:
one or more epoxidized alkoxysilane having alkoxy groups which are directly linked to the silicon atom;
a hydrolyzable, non-epoxidized silane;
colloidal silica;
a catalyst which promotes cleavage of an epoxy bond; and
at least one fluorinated hydrolyzable alkylsilane; and its use in coating substrates and a method for preparing such a coating.